Well, so far, Derpy's been starting things off pretty simple, huh? I get the feeling that she will use her new powers to ramp things up really quickly, though. So, let's see where everything goes from here...

Derpy had acquired Arbmos' knowledge during her night's sleep. Upon waking, she instantly knew about what to do for new types of magic.

"So... today's Monday." Derpy said. "I wonder what I should do today."

"Mayhaps you should head out and hone your magic skills?" Arbmos suggested. "It never hurts to get some practice in..."

"Okay!" Derpy said.

With that, Derpy headed out, looking for things to practice on. The best she could tell, she had gained a stronger sense of mind-control and persuasion. Whom she was going to test it out on, she had no idea, especially since it seemed a little demented.

"I don't know about this..." Derpy said. "...why would I want to control somepony's mind?"

"You'd be surprised at the... amusing things you can make them do." Arbmos said.

Derpy happened to notice that the Ponyville Post Office was up ahead. Parcel Post was outside having a brief word with Captain Express. Knowing what she could make them do from yesterday, she decided to have a quick look.

"Ditzy?" Captain Express said. "What are you doing here?"

Parcel turned his head away very rudely. "I wish not to associate myself with a clumsy, broken foal." he said. "You might as well be living with earthworms!"

Derpy's eyes widened at the comment... and momentarily glowed green on the sclerae. Almost immediately, she made an evil smile as her invisible horn glowed yellow. Parcel's eyes glowed the same color as he became immobile and emotionless.

"Yeah? Well, you think you're an earthworm, Parcel!" Derpy said very sternly.

The glow in Parcel's eyes went out, and after a moment, half-closed them and began making strange slurred sounds while weirdly moving his jaw. He began squirming on the ground and started eating the grass. Captain Express was in complete shock.

"Ditzy, what ever are you doing?" He asked.

Derpy's horn glowed again as she used mind-control on Captain Express. "You think you're... a lawn sprinkler." she said.

After the glow in his eyes went out, Captain Express held a very blank expression as he began to slowly turn to his left. "Pwp-pwp-pwp-pwp-pwp-pwp-pwp...!" he said while doing this. After a few seconds, he turned to his right a little quicker while going "p-t-t-t-t-t-t-t-t-t-t-t...!" and repeating the cycle over and over.

Derpy snickered at the sight of these two buffoons she made look like even bigger idiots. She then went along through Ponyville, feeling absolutely no remorse for what she had done. Instead, she felt very satisfied. Surprisingly, it seemed like mind-control was not all that unethical to her anymore.

It was sometime later that Derpy came across Snips and Snails.

"Ah, Derpy!" Snails said. "We heard you lost the mail and everypony got mad at you."

"Yeah, so we was thinkin' maybe you'd like to join our little outcast alliance?" Snips said.

"Yeah, we provide comfort to each other for our failures in the world." Snails said.

Derpy was about to say one thing, but after the whites of her eyes glowed green for a brief moment, she decided to say something else...

"Oh, that would be nice, but..." she said as her horn glowed, putting both Snips and Snails into a trance. "...you two think you're a pair of..." she smirked. "...sassy backup singer mares!"

After coming out of their trance, Snips and Snails both stood side-by-side, and began to step in sort of a synchronized dance while singing:

"Ain't got no time for my stal-li-on,

Oh, no-no-no, no,

Ain't got no time for gen-tle-colts,

Oh, no-no-no, nooooooo..."

As Derpy walked away from the two now-brainwashed school-age Unicorns chuckling to herself, she happened to spot Lyra Heartstrings and Sweetie "Bon Bon" Drops walking up, both of them laughing at Snips and Snails.

"Oh, Derpy-y-y-y!" Lyra said while laughing. "I don't know what you did to those two, but you got 'em goo-o-o-o-o-o-o-d!"

"Totally!" Bon Bon said. "Heh heh heh, mind telling us how you were able to make them do that? Ha, ha ha!"

Derpy did not answer; her eyes flashed green again, and she used mind-control once again one the two mares.

"GENTLECOLTS!" Derpy said very sternly to the two. "ARE-YOU-READY-TO-SERVE-UNDER-THE-CANTERLOT-ROYAL-GUARD!?"

Lyra and Bon Bon both held up their forehooves in a salute. "Ma'am, yes ma'am!" they both responded simultaneously.

"TIME-TO-GET-YOUR-WORTHLESS-SELVES-INTO-SHAPE!" Derpy said, before raising her hoof and pointing it down. "DROP-AND-GIVE-ME-FIVE-THOUSAND!"

"Ma'am, yes ma'am!" Lyra and Bon Bon both said, saluting before setting back their hind legs and started doing pushups. "One! Two! Three! Four! Five...!" they began counting with each one.

As Derpy walked off, she could not help but feel more and more satisfied with each victim she created from the Ponyville residents.

"I think I could get used to this..." Derpy said. "...I can bring everypony who wrongs me to their knees!"

Derpy began to laugh very evilly... and her eyes began to glow a green color in the sclerae once again.

That's it, my dear... Arbmos thought. ...keep honing your skills. You will need them. The more you can adjust your mortal body, the more I will have you under my hoof... and once I have you... heh heh heh.

(XXXX)

Twilight Sparkle was walking through Ponyville to take a break from her work.

"Well, being the Princess of Friendship is no easy task..." She said to herself. "...but I can't let Princess Celestia down!"

After walking for a bit, Twilight happened to notice Parcel Post squirming around in the dirt, appearing to be eating it. Captain Express was rotating back and forth, making strange noises... almost like a sprinkler.

"What the...?" Twilight said to herself.

She used her horn to sense for any magical presence around them. And she found...

"...they're under a spell!" Twilight said.

With that, the Alicorn walked over to them, angled her horn at them, closed her eyes, and made a flash of white light. Immediately, Parcel looked around, and then started spitting out the dirt he was eating in disgust. Captain Express looked confused.

"Huh? What's going on around here?" Captain Express asked.

"Gah! Disgusting!" Parcel said as he wiped his tongue.

"What's going on? What happened?" Twilight asked.

Captain Expressed looked over at Twilight in surprise. "Oh! Princess Twilight! Wait... where's Ditzy? She was here just now..."

"Derpy was around here? When?" Twilight asked.

"Well, let's see... I was given Parcel a few pointers... then Ditzy came up... said something about Parcel thinking he was an earthworm, followed by him doing it..." he paused and closed his eyes. "...I do not remember the rest."

"Hmmm..." Twilight pondered. "...maybe if I find Derpy, she can explain what happened."

With that, Twilight took off in the direction she assumed Derpy went off to.

"Peculiar..." Captain Express said. "...something is rather... off about Ditzy today, more so than usual."

Parcel's stomach groaned. He put his hoof on it.

"Oh, dear..." Parcel said with an ill look on his face. "...I'm gonna chunder!"

With that, he ran towards the nearest bush... and made some straining noises accompanied by a sloshing sound.

(XXXX)

Twilight continued through Ponyville to find Snips and Snails singing and dancing... and Twilight, after listening, realized it was a very feminine song and dance.

"They've had it, too!" Twilight said after sensing the magic on them.

She used the same spell again to free them. They both panted.

"Woah... who knew singing and dancing for fourteen minutes straight could take so much outta ya?" Snips asked.

"I don't know..." Snails responded. "...oh, Twilight!"

"What happened to you two?" Twilight asked.

"Well, Derpy just appeared, told us to act like singing and dancing mares... and we ended up just... doing it, without wanting to do it." Snips said.

"Derpy? She did this?" Twilight asked.

"Guess so..." Snails said.

Twilight immediately ended up with a suspicious look on her face.

"Well, I'd better see if I can catch up with her!" Twilight said, before heading off again. "What the hay is going on? Is Derpy really the one doing all this? She can't use magic!"

A little while later, Twilight found Lyra and Bon Bon doing pushups... very slowly and fatigued-looking.

"...four-hundred ninety-six... four-hundred ninety-seven... four-hundred ninety-eight..." they both said slowly.

Twilight used the counterspell on them, and they both collapsed to the ground, panting heavily.

"...Wh-why do my... forelegs... feel like... butter...?" Lyra asked.

"...Can't t-talk..." Bon Bon strained. "...s-so much... pain..."

"Girls, did Derpy do this?" Twilight asked.

"...Uh-huh..." the two uttered.

"Alright, thanks!" Twilight said, before continuing her on way.

After laying for a little while, Lyra and Bon Bon eventually started to push themselves on their hind legs back in the direction they came (much like how Sweetie Belle does whenever she's bored).

(XXXX)

Twilight arrived at Sugarcube Corner, where she happened to spot Derpy in the window. She went inside to see that Derpy appeared to be making Mr. and Mrs. Cake serve her really high-end pastries and other sweets... all without Derpy paying. Twilight also happened to notice a yellowish glow over Derpy's forehead, as well as the same glow in the Cakes' eyes.

"Prepare me another tray of apple tarts and fifty servings of tiramisu, my servants!" Derpy demanded.

The Cakes bowed to her. "As thou commandeth, Thy Benevolence." Mr. Cake said in a medieval Canterlot accent.

"Oh, and muffins! Lemon surprise! A hundred years' worth! Make that the main thing!" Derpy added.

"But of course, Thy Eminence." Mrs. Cake said in the same accent.

"Oh, dear..." Doctor Whooves, who just happened to be inside watching Derpy, said. "...I believe I should be going."

"Yo, doc!" Derpy said, using mind-control on Doctor Whooves. "You think you're a hot, runaway, model mare!"

After coming out of his brief trance, Doctor Whooves started making some very feminine poses.

"Work it... oh, work it... oh yeah!" Doctor Whooves said in a disturbingly seductive tone. He turned his attention to Twilight. "Wanna catch my image...? My good side...?" He said, turning his flank slightly towards her. "...My great side...?" He faced his plot directly at her.

Twilight, with her weird-out meter on overload, hastily rushed off from the brainwashed, posing Doctor Whooves. She walked right up to Derpy.

"Derpy," Twilight began. "what's been going on with you?"

"Ah, Twilight Sparkle!" Derpy began.

Twilight noticed a distinctive green glow in her eyes' sclerae for a brief moment, just as she was about to use the same spell on Twilight. However, the Alicorn was quick to react and put a spell on Derpy that would normally stop Unicorns from using magic. Glowing silver strands covered the invisible horn on Derpy's head.

"Okay, Derpy. In exactly one minute, the Binding Spell I just put on you will break." Twilight said. "And within that time, you will tell me what's going on."

"Okay..." Derpy began. "...but can you keep a secret?"

Twilight nodded. "Alright. What is it?"

"Well..." Derpy began, appearing to lift from her demonic persona she had upon Twilight entering. "...remember when I told you about Arbmos?"

"That spirit in your head? Yeah." Twilight said.

"Well, he's been teaching me about magic... because his horn is on my head!" Derpy said. "He just made it invisible so nopony would notice that I'm an Alicorn, like you!"

Twilight was shocked by this. "His horn... is on your head!? And how did it get invisible!?" She asked.

"Oh, Arbmos did it for me." Derpy said.

"But, how?" Twilight asked. "Using magic to affect the horn itself is very advanced! Even Princess Celestia has had trouble trying to do it herself!"

"Well, what's so bad about it?" Derpy asked.

"Well, I mean..." Twilight began. "...are you sure you can trust him? An entity that can use powerful magic... that sounds kinda shady to me."

Derpy began to wonder... what exactly was the reasoning behind all of this? Why exactly was Arbmos helping her to begin with? What was in it for him? Why did he want those books from the Canterlot Archives?

"ENOUGH!" Came Arbmos' voice in Derpy's head.

Two wisps of glowing violet smoke came out of Derpy's eyes for a split second, accompanied by a deep pulse in her ears, and she let out a short shriek at it happened. She hung her head down with a hoof on her chest, panting.

"Derpy, are you okay?" Twilight asked.

"Ngh... Twilight..." Derpy said, just before her eyes glowed green, not for a moment, but constantly. She looked up at Twilight with as best of an angry glare as her crossed eyes would allow.

"...leave me alone, you nosy brunt!" Derpy finished.

Just as Twilight was about to berate Derpy for her behavior, the magic bind around Arbmos' invisible horn vanished, and then, Derpy vanished in a flash of crimson light.

"Gr, she teleported!" Twilight said. "There's something seriously wrong here!"

"Twilight! Twilight!" Spike said as he came running through the front door of Sugarcube Corner. "I just belched up this letter from the Princess!"

"Oh, good. Let me see it." Twilight said, taking the letter and opening it.

Dearest Twilight,

I regret to interrupt you should you be attending to any important matters, but this is of utmost urgency. Last night, the Canterlot Archives were burglarized; three books were stolen from the restricted wing. The Book of Unity, the Book of Influence, and the Book of Superiority. The guards searched the premises, but found no signs of the thief. Though the investigation is still ongoing, I strongly caution you to keep a close eye out for any suspicious characters lurking around Ponyville. These three books, in the wrong hands, could prove to be devastating. Send me a letter immediately if you notice ANYTHING out of the ordinary. Do take care, and stay safe!

Your honorary teacher,

Princess Celestia.

"Uh-oh... this isn't good." Twilight said. "The Archives have been robbed!"

"So, what are you gonna be able to do about it?" Spike asked.

Twilight shuffled her hooves nervously. "Ngh... I don't want to think Derpy did it..." she uttered.

"WHAT?" Spike said. "You think Ditzy broke in? She can't even put a key into a keyhole without messing up over and over!"

"Well... Derpy's been given special... abilities." Twilight said. "She's encountered Arbmos... that new spirit I've been trying to learn about."

"I'd call it obsessing over..." Spike said. "...so, do you think we should tell the Princess if that's what you think?"

"...No. Not yet." Twilight said.

"What! Why?" Spike asked. "The Princess said it was really important!"

"I need to look into this a little more, Spike! We need to know exactly what we're up against!" Twilight said. She began racking her brain. "Arbmos... Arbmos... ngh, why is this so difficult!? I can't find anything on that name!"

"Well, would you like to head back to the castle to try and look into it?" Spike asked.

"Well... first I need to fix everypony that Derpy's messed up." Twilight said, looking around Sugarcube Corner.

Well, Derpy's been taking things for a bit of a turn, huh? Who knows how long it will be before worse comes to worst? For now, though, we'll just have to wait it out and see where things go. Keep holding on...